/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.lucene.spatial.tier;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TermDocs;
import org.apache.lucene.search.DocIdSet;
import org.apache.lucene.search.Filter;
import org.apache.lucene.util.NumericUtils;
import org.apache.lucene.util.OpenBitSet;

import java.io.IOException;
import java.util.List;

/**
 * CartesianShapeFilter is a proper Lucene filter that filters out documents
 * that are not within the boxes that define a certain Shape overlaps. For
 * example, if a shape overlaps boxes 1, 3 and 6, then a document that has been
 * plotted to be within box 5 will be filtered out.
 */
public class CartesianShapeFilter extends Filter {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	private final Shape shape;
	private final String fieldName;

	/**
	 * Creates a new CartesianShapeFilter that will filter out documents that
	 * are not within the boxes defined in the given Shape. The Filter will
	 * check the values of the given field to see whether a document is within a
	 * certain box.
	 * 
	 * @param shape
	 *            Shape containing boxes that documents must be within, in order
	 *            not to be filtered out
	 * @param fieldName
	 *            Name of the field in the documents that will be checked for
	 *            what boxes the document is in
	 */
	public CartesianShapeFilter(Shape shape, String fieldName) {
		this.shape = shape;
		this.fieldName = fieldName;
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
		OpenBitSet bits = new OpenBitSet(reader.maxDoc());

		TermDocs termDocs = reader.termDocs();
		List<Double> boxIds = shape.getBoxIds();
		for (double boxId : boxIds) {
			termDocs.seek(new Term(fieldName, NumericUtils
					.doubleToPrefixCoded(boxId)));

			// iterate through all documents which have this boxId
			while (termDocs.next()) {
				bits.fastSet(termDocs.doc());
			}
		}
		return bits;
	}
}
